The present invention concerns a sensor that provides a signal that varies with motion (translation or rotation) according to a function such as a voltage transfer function. More specifically, the invention relates to a linear position sensor and a control for such linear position sensor.
The present invention concerns position sensors for use with a motor vehicle. Due to the highly competitive nature of the business of supplying components to the automotive industry, any vehicle based sensor must by reliable, accurate and cost competitive.
A number of prior art patents relate to position sensors. U.S. Pat. No. 3,020,527 to MacLaren concerns a position indicating system and more particularly concerns a telemetric system for indication the position of a remote or inaccessible means which may be moved to various positions in a simple, convenient, accurate, and reliable manner.
U.S. Pat. No. 4,555,120 to Frait et al concerns a position sensor which can be utilized as a height sensor in an automatic vehicle suspension system. The structure disclosed in the ""120 patent to Frait et al is principally concerned with the sensor structure.
Position sensing apparatus constructed in accordance with the present invention includes an elongated field producing member having an input for energizing the field producing member to produce an electromagnetic field in the vicinity of the field producing member. An elongated field responsive member oriented generally parallel to the field producing member along a length of the field producing member provides an output signal in response to the electromagnetic field produced by the field producing member. A coupling member supported for relative movement with respect to one of the elongated field producing or field responsive members alters a response of the field responsive member as the coupling member moves. This altering changes the signal at the output of the field responsive member.
A monitoring circuit coupled to the output from the field responsive member correlates changes in the output signal with relative movement of the coupling member. The monitoring circuit includes a memory for modifying the output signal from the field responsive member to provide a position signal having a controlled relation to relative movement of the coupling member.
In accordance with a preferred embodiment of the invention the controlled relation is a linear relation so that the modified output from the monitoring circuit is directly proportion of the position of the coupling member.
The monitoring circuit is most preferably a programmable controller having a control program for gathering data from an output from the field responsive member. The modification of the output signal from the field responsive member is most preferably accomplished with an electronically erasable read only memory circuit. This circuit selectively adds or subtracts a value to the output from the field responsive member based upon the value of that output.
The preferred use of the position sensor is in a ride control system for use with a motor vehicle. The ride control system is most preferably implemented with a pressure adjusted height adjusting means such as pressurized shock absorbers. The pressurized shock absorbers are coupled to a pressure source and a valving control to control the extension or height of the vehicle.
A further feature of the invention is the use of a pressure sensor to determine pressure in the shock absorber and correlate the pressure and shock absorber extension to determine a failure of the shock absorber. A further feature is adjustment of the ride level of the motor vehicle based upon sensed pressure and position of the shock absorber. If a certain pressure is required to maintain a specified spacing between shock absorber components, it may be assumed the load is high and therefore the handling characteristics of the vehicle may be improved by lowering the center of gravity. Use of a programmable controller allows the use of control programs to achieve control over vehicle ride that can be readily updated by reprogramming the controller.
The above and other objects advantages and features of the invention will be better understood from the following detailed description of a preferred embodiment of the invention which is described in conjunction with the accompanying drawings.